Fentanyl is an opioid analgesic that is roughly one-hundred fold more potent than morphine. Chemically, it is a 1,4-disubstituted piperidine molecule with agonist properties at the (D-opioid receptor. This type of receptor is found in the brain as well as in various peripheral tissues and in the spinal chord. A transdermal delivery system for fentanyl has been described. This system delivers fentanyl at rates between 25 and 100 Φg/hour. Due to severe side effects, the fentanyl transdermal system described in the art is indicated only in the management of chronic pain in patients requiring continuous opioid analgesia for pain that cannot be managed by lesser means. Because serious or life-threatening hypoventilation could occur, the use of fentanyl transdermal treatment is strongly contraindicated in children younger than 12 years of age, in the management of acute or post-operative pain, including use in outpatient surgery, and in general in any situation where pain can be managed by non-opioid therapy.
The development of a short-acting transdermal fentanyl analog system would be of great value. A soft fentanyl analog has been described in the art. Remifentanyl (Ultiva) is marketed by GlaxoWellcome as an ultrashort acting opioid for intravenous analgesia in anaesthetic cocktails. Due to its high degree of efficiency against extreme pain, a safe soft analog of fentanyl could be used in cases of pain management that are not presently suitable for the current opioid therapy.